diff --git a/inc/Lau1DCubicSpline.hh b/inc/Lau1DCubicSpline.hh
index 39c22c8..e9a258f 100644
--- a/inc/Lau1DCubicSpline.hh
+++ b/inc/Lau1DCubicSpline.hh
@@ -1,301 +1,302 @@
 
 /*
 Copyright 2015 University of Warwick
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 
     http://www.apache.org/licenses/LICENSE-2.0
 
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
 
 /*
 Laura++ package authors:
 John Back
 Paul Harrison
 Thomas Latham
 */
 
 /*! \file Lau1DCubicSpline.hh
     \brief File containing declaration of Lau1DCubicSpline class.
  */
 
 /*! \class Lau1DCubicSpline
     \brief Class for defining a 1D cubic spline based on a set of knots.
 
     Class for defining a 1D cubic spline based on a set of knots.
     Interpolation between the knots is performed either by one of
     two types of cubic spline (standard or Akima) or by linear interpolation.
     The splines are defined by a piecewise cubic function which, between knots i and i+1, has the form
 
     f_i(x) = (1 - t)*y_i + t*y_i+1 + t*(1 - t)(a*(1 - t) + b*t)
 
     where t = (x - x_i)/(x_i+1 - x_i),
     a =  k_i  *(x_i+1 - x_i) - (y_i+1 - y_i),
     b = -k_i+1*(x_i+1 - x_i) + (y_i+1 - y_i)
 
     and k_i is (by construction) the first derivative at knot i.
     f(x) and f'(x) are continuous at the internal knots by construction.
 
     For the standard splines, f''(x) is required to be continuous
     at all internal knots placing n-2 constraints on the n parameters, k_i.
     The final two constraints are set by the boundary conditions.
     At each boundary, the function may be:
 
     (i)   Clamped :     f'(x) = C at the last knot
     (ii)  Natural :     f''(x) = 0 at the last knot
     (iii) Not a knot :  f'''(x) continuous at the second last knot
 
     The algorithms used in these splines can be found on:
     http://en.wikipedia.org/wiki/Spline_interpolation#Algorithm_to_find_the_interpolating_cubic_spline
     http://en.wikipedia.org/wiki/Tridiagonal_matrix_algorithm
 
     For the Akima splines, the values of k_i are determined from the slopes of the four nearest segments (a_i-1, a_i, a_i+1 and a_i+2) as
 
     k_i = ( | a_i+2 - a_i+1 | a_i  +  | a_i - a_i-1 | a_i+1 ) / ( | a_i+2 - a_i+1 |  +  | a_i - a_i-1 | )
 
     and as
 
     k_i = ( a_i + a_i+1 ) / 2
 
     in the special case a_i-1 == a_i != a_i+1 == a_i+2.
 
     Boundary conditions are specified by the relations
     a_2 - a_1 = a_1 - a_0 = a_0 - a_-1 and
     a_n-1 - a_n-2 = a_n - a_n-1 = a_n+1 - a_n
 
     The algorithms used in these splines can be found in:
     J.ACM vol. 17 no. 4 pp 589-602
  */
 
 #ifndef LAU_1DCUBICSPLINE
 #define LAU_1DCUBICSPLINE
 
-#include <vector>
 #include <array>
+#include <memory>
+#include <vector>
 
 #include <nlohmann/json.hpp>
 
 #include "Rtypes.h"
 #include "TF1.h"
 #include "TFitResultPtr.h"
 
 #include "LauPrint.hh"
 
 class TH1;
 class LauAbsRValue;
 class LauParameter;
 
 class Lau1DCubicSpline final {
 
 	public:
 		//! Define the allowed interpolation types
 		enum class SplineType {
 			StandardSpline, /*!< standard cubic splines with f''(x) continuous at all internal knots */
 			AkimaSpline, /*!< Akima cubic splines with f'(x) at each knot defined locally by the positions of only five knots */
 			LinearInterpolation /*! Linear interpolation between each pair of knots */
 		};
 
 		//! Define the allowed boundary condition types
 		/*!
 		    These are only supported by standard splines
 		*/
 		enum class BoundaryType {
 			Clamped, /*!< clamped boundary - f'(x) = C */
 			Natural, /*!< natural boundary - f''(x) = 0 */
 			NotAKnot /*!< 'not a knot' boundary - f'''(x) continuous at second last knot */
 		};
 
 		//! Constructor
 		/*!
 		    \param [in] xs the x-values of the knots
 		    \param [in] ys the y-values of the knots
 		    \param [in] type the type of spline (Standard, Akima, Linear)
 		    \param [in] leftBound the left-hand boundary condition
 		    \param [in] rightBound the right-hand boundary condition
 		    \param [in] dydx0 the gradient at the left-hand boundary of a clamped spline
 		    \param [in] dydxn the gradient at the right-hand boundary of a clamped spline
 		*/
 		Lau1DCubicSpline(const std::vector<Double_t>& xs, const std::vector<Double_t>& ys,
 				 const SplineType type = SplineType::StandardSpline,
 				 const BoundaryType leftBound = BoundaryType::NotAKnot,
 				 const BoundaryType rightBound = BoundaryType::NotAKnot,
 				 const Double_t dydx0 = 0.0, const Double_t dydxn = 0.0);
 
 		//! Evaluate the function at given point
 		/*!
 		    \param [in] x the x-coordinate
 		    \return the value of the spline at x
 		*/
 		Double_t evaluate(const Double_t x) const;
 
 		//! Update the y-values of the knots
 		/*!
 		    \param [in] ys the y-values of the knots
 		*/
 		void updateYValues(const std::vector<Double_t>& ys);
 		//! Update the y-values of the knots
 		/*!
 		    \param [in] ys the y-values of the knots
 		*/
 		void updateYValues(const std::vector<LauParameter*>& ys);
 		//! Update the y-values of the knots
 		/*!
 		    \param [in] ys the y-values of the knots
 		*/
 		void updateYValues(const std::vector<LauAbsRValue*>& ys);
 
 		//! Update the type of interpolation to perform
 		/*!
 		    \param [in] type the type of interpolation
 		*/
 		void updateType(const SplineType type);
 
 		//! Update the boundary conditions for the spline
 		/*!
 		    \param [in] leftBound the left-hand boundary condition
 		    \param [in] rightBound the right-hand boundary condition
 		    \param [in] dydx0 the gradient at the left-hand boundary of a clamped spline
 		    \param [in] dydxn the gradient at the right-hand boundary of a clamped spline
 		*/
 		void updateBoundaryConditions(const BoundaryType leftBound,
 					      const BoundaryType rightBound,
 					      const Double_t dydx0 = 0.0,
 					      const Double_t dydxn = 0.0);
 
 		//! Get the number of knots
 		std::size_t getnKnots() const {return nKnots_;}
 
 		//! Get y values
 		const std::vector<Double_t>& getYValues() const {return y_;}
 
 		//! Get x values
 		const std::vector<Double_t>& getXValues() const {return x_;}
 
 		//! Get the coefficients of a given spline segment in the form a + bx + cx^2 + dx^3
 		/*!
 			\param [in] segIndex refers to the index of the knot at the left end of the segment (segIndex = 0 gets the coefficients of the the segment between x_0 and x_1)
 			\param [in] normalise if true, the coefficients returned will be normalised by the integral of the complete spline (defaults to false)
 			\return coefficients {a, b, c, d}
 		*/
 		std::array<Double_t,4> getCoefficients(const std::size_t segIndex, const bool normalise = false) const;
 
 		//! Get the integral over all the spline segments
 		Double_t integral() const;
 
 		//! Make a TF1 showing the spline with its current knot values
 		/*!
 			\param [in] normalise whether or not you want the spline normalised
 			\return 1D function object
 		*/
 		TF1* makeTF1(const bool normalise = false) const;
 
 		//! Fit the the normalisation of the spline to a TH1
 		/*!
 			\param [in] hist the histogram to be fitted
 			\param [in] printLevel the level of printout desired from fit
 			\return a TF1 fit to the histogram
 		*/
 		TF1* normaliseToTH1(TH1* hist, const LauOutputLevel printLevel = LauOutputLevel::Standard) const;
 
 		//! Fit the spline to a TH1
 		/*!
 			\param [in] hist the histogram to be fitted
 			\param [in] printLevel the level of printout desired from fit
 			\param [in] doWL If true do a weighted likelihood fit, else chi2
 			\return a shared-ownership smart pointer to the fit results
 		*/
 		TFitResultPtr fitToTH1(TH1* hist, const LauOutputLevel printLevel = LauOutputLevel::Standard, const bool doWL = false);
 
 		//! Set spline variables to those read from a json file
 		/*
 			\param[in] fileName the name of the file from which the JSON should be read
 			\param[in] splineName the (optional) name of the entry in the JSON from which the spline should be read
 			\return the newly constructed spline
 		*/
-		static Lau1DCubicSpline readFromJson(const TString& fileName, const TString& splineName = "");
+		static std::unique_ptr<Lau1DCubicSpline> readFromJson(const TString& fileName, const TString& splineName = "");
 
 		//! Write the spline to a json file using nlohmann json
 		/*!
 			\param[in] fileName the name of the file to which the JSON should be written
 			\param[in] splineName the (optional) name of the entry in the JSON to which the spline should be written
 			\param[in] append if true, append the spline to the existing JSON within the file - if using this option it is then mandatory to provide splineName
 		*/
 		void writeToJson(const TString& fileName, const TString& splineName = "", const bool append = false) const;
 
 	private:
 		//! Default constructor - only for use in readFromJson
 		Lau1DCubicSpline() = default;
 
 		//! Initialise the class
 		void init();
 
 		//! Calculate the first derivative at each knot
 		void calcDerivatives();
 
 		//! Calculate the first derivatives according to the standard method
 		void calcDerivativesStandard();
 		//! Calculate the first derivatives according to the Akima method
 		void calcDerivativesAkima();
 
 		//! The number of knots in the spline
 		std::size_t nKnots_{0};
 
 		//! The x-value at each knot
 		std::vector<Double_t> x_;
 		//! The y-value at each knot
 		std::vector<Double_t> y_;
 		//! The first derivative at each knot
 		std::vector<Double_t> dydx_;
 
 		//! The 'a' coefficients used to determine the derivatives
 		std::vector<Double_t> a_;
 		//! The 'b' coefficients used to determine the derivatives
 		std::vector<Double_t> b_;
 		//! The 'c' coefficients used to determine the derivatives
 		std::vector<Double_t> c_;
 		//! The 'd' coefficients used to determine the derivatives
 		std::vector<Double_t> d_;
 
 		//! The type of interpolation to be performed
 		SplineType type_{SplineType::StandardSpline};
 
 		//! The left-hand boundary condition on the spline
 		BoundaryType leftBound_{BoundaryType::NotAKnot};
 		//! The right-hand boundary condition on the spline
 		BoundaryType rightBound_{BoundaryType::NotAKnot};
 
 		//! The gradient at the left boundary for a clamped spline
 		Double_t dydx0_{0.0};
 		//! The gradient at the right boundary for a clamped spline
 		Double_t dydxn_{0.0};
 
 		// JSON serialisation stuff
 
 		// map SplineType values to JSON as strings
 		NLOHMANN_JSON_SERIALIZE_ENUM( SplineType, {
 				{SplineType::StandardSpline, "StandardSpline"},
 				{SplineType::AkimaSpline, "AkimaSpline"},
 				{SplineType::LinearInterpolation, "LinearInterpolation"},
 				})
 
 		// map BoundaryType values to JSON as strings
 		NLOHMANN_JSON_SERIALIZE_ENUM( BoundaryType, {
 				{BoundaryType::Clamped, "Clamped"},
 				{BoundaryType::Natural, "Natural"},
 				{BoundaryType::NotAKnot, "NotAKnot"},
 				})
 
 		// enable serialisation of this class
 		NLOHMANN_DEFINE_TYPE_INTRUSIVE(Lau1DCubicSpline, nKnots_, x_, y_, type_, leftBound_, rightBound_, dydx0_, dydxn_)
 
 		ClassDef(Lau1DCubicSpline, 0) // Class for defining a 1D cubic spline
 };
 
 #endif
diff --git a/src/Lau1DCubicSpline.cc b/src/Lau1DCubicSpline.cc
index 56aedcb..f382ebb 100644
--- a/src/Lau1DCubicSpline.cc
+++ b/src/Lau1DCubicSpline.cc
@@ -1,660 +1,660 @@
 
 /*
 Copyright 2015 University of Warwick
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 
     http://www.apache.org/licenses/LICENSE-2.0
 
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
 
 /*
 Laura++ package authors:
 John Back
 Paul Harrison
 Thomas Latham
 */
 
 /*! \file Lau1DCubicSpline.cc
   \brief File containing implementation of Lau1DCubicSpline class.
  */
 
 #include <cmath>
 #include <cstdlib>
 #include <fstream>
 #include <iostream>
 
 #include <nlohmann/json.hpp>
 
 #include <TH2.h>
 #include <TSystem.h>
 
 #include "Lau1DCubicSpline.hh"
 #include "LauAbsRValue.hh"
 #include "LauParameter.hh"
 
 ClassImp(Lau1DCubicSpline)
 
 
 Lau1DCubicSpline::Lau1DCubicSpline(const std::vector<Double_t>& xs, const std::vector<Double_t>& ys,
 				   const SplineType type,
 				   const BoundaryType leftBound,
 				   const BoundaryType rightBound,
 				   const Double_t dydx0, const Double_t dydxn) :
 	nKnots_{xs.size()},
 	x_{xs},
 	y_{ys},
 	type_{type},
 	leftBound_{leftBound},
 	rightBound_{rightBound},
 	dydx0_{dydx0},
 	dydxn_{dydxn}
 {
 	init();
 }
 
-Lau1DCubicSpline Lau1DCubicSpline::readFromJson(const TString& filename, const TString& splineName)
+std::unique_ptr<Lau1DCubicSpline> Lau1DCubicSpline::readFromJson(const TString& filename, const TString& splineName)
 {
 	using nlohmann::json;
 
 	std::ifstream in(filename, std::ios_base::in);
 	if ( not in ) {
 		std::cerr << "ERROR in Lau1DCubicSpline::readFromJson : couldn't open file \"" << filename << "\"" << std::endl;
-		// TODO - need to check that this puts it into a sensibly defined state
-		return Lau1DCubicSpline{};
+		return std::unique_ptr<Lau1DCubicSpline>{};
 	}
 
 	json j;
 	in >> j;
 
 	if ( splineName != "" ) {
 		j = j[splineName.Data()];
 	}
 
-	Lau1DCubicSpline spline;
-	j.get_to(spline);
-	spline.init();
+	// NB can't use std::make_unique here because the default constructor is private
+	std::unique_ptr<Lau1DCubicSpline> spline{ new Lau1DCubicSpline };
+	j.get_to(*spline);
+	spline->init();
 
 	return spline;
 }
 
 void Lau1DCubicSpline::writeToJson(const TString& filename, const TString& splineName, const bool append) const
 {
 	using nlohmann::json;
 
 	// if we're appending, we need to first load in the exising JSON from the file
 	json j;
 	if ( append ) {
 		// if appending we must have a name, so check that first
 		if ( splineName == "" ) {
 			std::cerr << "ERROR in Lau1DCubicSpline::writeToJson : when appending to a file it is mandatory to give a name to the spline" << std::endl;
 			return;
 		}
 
 		std::ifstream in{filename, std::ios_base::in};
 		if ( not in ) {
 			std::cerr << "ERROR in Lau1DCubicSpline::writeToJson : couldn't open file \"" << filename << "\" for initial reading" << std::endl;
 			return;
 		}
 
 		in >> j;
 	}
 
 	if(splineName == "") {
 		j = *this;
 	} else {
 		j[splineName.Data()] = *this;
 	}
 
 	// now we can overwrite the file
 	std::ofstream out{filename, std::ios_base::out};
 	if(not out) {
 		std::cerr << "ERROR in Lau1DCubicSpline::writeToJson : couldn't open file \"" << filename << "\" for writing. No file will be written!" << std::endl;
 		return;
 	}
 
 	out << j.dump(4);
 	out << std::endl;
 	out.close();
 
 	return;
 }
 
 Double_t Lau1DCubicSpline::evaluate(const Double_t x) const
 {
 	// do not attempt to extrapolate the spline
 	if( x<x_[0] || x>x_[nKnots_-1] ) {
 		std::cerr << "WARNING in Lau1DCubicSpline::evaluate : function is only defined between " << x_[0] << " and " << x_[nKnots_-1] << std::endl;
 		std::cerr << "                                        value at " << x << " returned as 0" << std::endl;
 		return 0.;
 	}
 
 	// first determine which 'cell' of the spline x is in
 	// cell i runs from knot i to knot i+1
 	std::size_t cell{0};
 
 	while( x > x_[cell+1] ) {
 		++cell;
 	}
 
 	// obtain x- and y-values of the neighbouring knots
 	const Double_t xLow  { x_[cell] };
 	const Double_t xHigh { x_[cell+1] };
 	const Double_t yLow  { y_[cell] };
 	const Double_t yHigh { y_[cell+1] };
 
 	if(type_ == SplineType::LinearInterpolation) {
 		return yHigh*(x-xLow)/(xHigh-xLow) + yLow*(xHigh-x)/(xHigh-xLow);
 	}
 
 	// obtain t, the normalised x-coordinate within the cell,
 	// and the coefficients a and b, which are defined in cell i as:
 	//
 	//      a_i =  k_i  *(x_i+1 - x_i) - (y_i+1 - y_i),
 	//      b_i = -k_i+1*(x_i+1 - x_i) + (y_i+1 - y_i)
 	//
 	// where k_i is (by construction) the first derivative at knot i
 	const Double_t t { (x - xLow) / (xHigh - xLow) };
 	const Double_t a {     dydx_[cell]   * (xHigh - xLow) - (yHigh - yLow) };
 	const Double_t b { -1.*dydx_[cell+1] * (xHigh - xLow) + (yHigh - yLow) };
 
 	const Double_t retVal { (1 - t) * yLow + t * yHigh + t * (1 - t) * ( a * (1 - t) + b * t ) };
 
 	return retVal;
 }
 
 void Lau1DCubicSpline::updateYValues(const std::vector<Double_t>& ys)
 {
 	y_ = ys;
 	this->calcDerivatives();
 }
 
 void Lau1DCubicSpline::updateYValues(const std::vector<LauParameter*>& ys)
 {
 	for (std::size_t i{0}; i<nKnots_; ++i){
 		y_[i] = ys[i]->unblindValue();
 	}
 	this->calcDerivatives();
 }
 
 void Lau1DCubicSpline::updateYValues(const std::vector<LauAbsRValue*>& ys)
 {
 	for (std::size_t i{0}; i<nKnots_; ++i){
 		y_[i] = ys[i]->unblindValue();
 	}
 	this->calcDerivatives();
 }
 
 void Lau1DCubicSpline::updateType(const SplineType type)
 {
 	if(type_ != type) {
 		type_ = type;
 		this->calcDerivatives();
 	}
 }
 
 void Lau1DCubicSpline::updateBoundaryConditions(const BoundaryType leftBound,
 		const BoundaryType rightBound,
 		const Double_t dydx0, const Double_t dydxn)
 {
 	bool updateDerivatives{false};
 
 	if(leftBound_ != leftBound || rightBound_ != rightBound) {
 		leftBound_ = leftBound;
 		rightBound_ = rightBound;
 		updateDerivatives = true;
 	}
 
 	if(dydx0_ != dydx0) {
 		dydx0_ = dydx0;
 		if(leftBound_ == BoundaryType::Clamped) updateDerivatives = true;
 	}
 
 	if(dydxn_ != dydxn) {
 		dydxn_ = dydxn;
 		if(rightBound_ == BoundaryType::Clamped) updateDerivatives = true;
 	}
 
 	if(updateDerivatives) {
 		this->calcDerivatives();
 	}
 }
 
 std::array<Double_t,4> Lau1DCubicSpline::getCoefficients(const std::size_t segIndex, const bool normalise) const
 {
 	std::array<Double_t,4> result = {0.,0.,0.,0.};
 
 	if(segIndex >= nKnots_-1)
 	{
 		std::cerr << "ERROR in Lau1DCubicSpline::getCoefficients requested for too high a knot value" << std::endl;
 		return result;
 	}
 
 	Double_t xL = x_[segIndex]   , xH = x_[segIndex+1];
 	Double_t yL = y_[segIndex]   , yH = y_[segIndex+1];
 	Double_t h = xH-xL; //This number comes up a lot
 
 	switch(type_)
 	{
 		case SplineType::StandardSpline:
 		case SplineType::AkimaSpline:
 			{
 				Double_t kL = dydx_[segIndex], kH = dydx_[segIndex+1];
 
 				//a and b based on definitions from https://en.wikipedia.org/wiki/Spline_interpolation#Algorithm_to_find_the_interpolating_cubic_spline
 				Double_t a = kL*h-(yH-yL);
 				Double_t b =-kH*h+(yH-yL);
 
 				Double_t denom = -h*h*h;//The terms have a common demoninator
 
 				result[0] = -b*xL*xL*xH + a*xL*xH*xH + h*h*(xL*yH - xH*yL);
 				result[1] = -a*xH*(2*xL+xH) + b*xL*(xL+2*xH) + h*h*(yL-yH);
 				result[2] = -b*(2*xL+xH) + a*(xL+2*xH);
 				result[3] = -a+b;
 
 				for(auto& res : result){res /= denom;}
 				break;
 			}
 /*		case SplineType::AkimaSpline: // Double check the Akima description of splines (in evaluate) right now they're the same except for the first derivatives
 			{
 				//using fomulae from https://asmquantmacro.com/2015/09/01/akima-spline-interpolation-in-excel/
 				std::function<Double_t(Int_t)> m = [&](Int_t j) //formula to get the straight line gradient
 				{
 					if(j < 0){return 2*m(j+1)-m(j+2);}
 					if(j >= nKnots_){return 2*m(j-1)-m(j-2);}
 					return (y_[j+1]-y_[j]) / (x_[j+1]-x_[j]);
 				};
 
 				auto t = [&](Int_t j)
 				{
 					Double_t res = 0.; //originally res was called 't' but that produced a shadow warning
 					Double_t denom = TMath::Abs(m(j+1)-m(j)) + TMath::Abs(m(j-1)-m(j-2));
 					if(denom == 0){res = (m(j)-m(j-1))/2;} //Special case for when denom = 0
 					else
 					{
 						res = TMath::Abs(m(j+1)-m(j))*m(j-1) + TMath::Abs(m(j-1)-m(j-2))*m(j);
 						res /= denom;
 					}
 					return res;
 				};
 
 				//These are the p's to get the spline in the form p_k(x-xL)^k
 				Double_t pDenom = x_[segIndex+1]/x_[segIndex]; //a denominator used for p[2] and p[3]
 				std::array<Double_t,4> p = {y_[segIndex],t(segIndex),0.,0.}; //we'll do the last 2 below
 
 				p[2] = 3*m(segIndex)-2*t(segIndex)-t(segIndex+1);
 				p[2]/= pDenom;
 
 				p[3] = t(segIndex)+t(segIndex+1)-2*m(segIndex);
 				p[3]/= pDenom*pDenom;
 
 				//Now finally rearranging the p's into the desired results
 				result[0] = p[0]-p[1]*xL+p[2]*xL*xL-p[3]*xL*xL*xL;
 				result[1] = p[1]-2*p[2]*xL+3*p[3]*xL*xL;
 				result[2] = p[2]-3*p[3]*xL;
 				result[3] = p[3];
 
 				break;
 			}*/
 		case SplineType::LinearInterpolation:
 			{
 				result[0] = xH*yL-xL*yH;
 				result[1] = yH-yL;
 
 				for(auto& res : result){res /= h;}
 				break;
 			}
 	}
 
 	if (normalise) {
 		const Double_t integral { this->integral() };
 		for(auto& res : result){res /= integral;}
 	}
 
 	return result;
 }
 
 Double_t Lau1DCubicSpline::integral() const
 {
 	Double_t integral{0.0};
 	for(std::size_t iKnot{0}; iKnot < nKnots_ -1; ++iKnot)
 	{
 		const Double_t minAbs { x_[iKnot] };
 		const Double_t maxAbs { x_[iKnot+1] };
 
 		const std::array<Double_t,4> coeffs { this->getCoefficients(iKnot, false) };
 
 		auto integralFunc = [&coeffs](Double_t x){return coeffs[0]*x + coeffs[1]*x*x/2.0 + coeffs[2]*x*x*x/3.0 + coeffs[3]*x*x*x*x/4.0;};
 
 		integral += integralFunc(maxAbs);
 		integral -= integralFunc(minAbs);
 	}
 	return integral;
 }
 
 TF1* Lau1DCubicSpline::makeTF1(const bool normalise) const
 {
 	auto fitf = [this](Double_t* x, Double_t* par) {//there is only 1 x (the abscissa) and 1 par (a scaling of the entire thing for normalisation)
 		return this->evaluate( x[0] ) * par[0];
 	};
 
 	//Make the function
 	TF1* func = new TF1("FittedFunc",fitf,x_.front(),x_.back(),1);
 
 	func -> SetParNames("Normalisation");
 	if(normalise)
 	{
 		func->SetParameter(0, 1./func->Integral(x_.front(),x_.back()));
 	}
 	else{func->SetParameter(0,1.);}
 
 	return func;
 }
 
 TF1* Lau1DCubicSpline::normaliseToTH1(TH1* hist, const LauOutputLevel printLevel) const
 {
 	//first define the fit function
 	auto fitf = [this](Double_t* x, Double_t* par) {//there is only 1 x (the abscissa) and 1 par (a scaling of the entire thing)
 		return this->evaluate( x[0] ) * par[0];
 	};
 	//Make the function
 	TF1* FittedFunc = new TF1("FittedFunc",fitf,x_.front(),x_.back(),1);
 	//Set the parameter name
 	FittedFunc -> SetParNames("Constant");
 	//Set the parameter limits and default value
 	FittedFunc -> SetParLimits(0,0.,10.);
 	FittedFunc -> SetParameter(0,1.);
 
 	// Options to:
 	// - N = do not store the graphics function
 	// - 0 = do not plot the fit result
 	TString fitOptions {"N 0"};
 
 	switch ( printLevel ) {
 		case LauOutputLevel::Verbose :
 			fitOptions += " V";
 			break;
 		case LauOutputLevel::Quiet :
 			fitOptions += " Q";
 			break;
 		case LauOutputLevel::Standard :
 			break;
 	}
 
 	hist->Fit( "FittedFunc", fitOptions );
 
 	return FittedFunc;
 }
 
 TFitResultPtr Lau1DCubicSpline::fitToTH1(TH1* hist, const LauOutputLevel printLevel, const bool doWL)
 {
 	auto fitf = [this](Double_t* x, Double_t* par) {
 		this -> updateYValues( std::vector<Double_t>(par, par + nKnots_) );
 		return this -> evaluate( x[0] );
 	};
 
 	TF1 FittedFunc("FittedFunc",fitf,x_.front(),x_.back(),nKnots_);
 
 	const Double_t knotMax { hist->GetMaximum() * 1.5 };
 
 	for(std::size_t knot{0}; knot <= nKnots_ ; ++knot)
 	{
 		FittedFunc.SetParName(knot, Form("Knot%lu",knot));
 		FittedFunc.SetParLimits(knot, 0., knotMax);
 		FittedFunc.SetParameter(knot, y_[knot]);
 	}
 
 	// Options to:
 	// - N = do not store the graphics function
 	// - 0 = do not plot the fit result
 	// - S = save the result of the fit
 	// - WL= do a weighted likelihood fit (not chi2)
 	TString fitOptions {"N 0 S"};
 	if(doWL){fitOptions += " WL";}
 
 	switch ( printLevel ) {
 		case LauOutputLevel::Verbose :
 			fitOptions += " V";
 			break;
 		case LauOutputLevel::Quiet :
 			fitOptions += " Q";
 			break;
 		case LauOutputLevel::Standard :
 			break;
 	}
 
 	return hist->Fit( "FittedFunc", fitOptions );
 }
 
 void Lau1DCubicSpline::init()
 {
 	if( y_.size() != x_.size()) {
 		std::cerr << "ERROR in Lau1DCubicSpline::init : The number of y-values given does not match the number of x-values" << std::endl;
 		std::cerr << "                                  Found " <<  y_.size() << ", expected " << x_.size() << std::endl;
 		gSystem->Exit(EXIT_FAILURE);
 	}
 
 	if( nKnots_ < 3 ) {
 		std::cerr << "ERROR in Lau1DCubicSpline::init : The number of knots is too small" << std::endl;
 		std::cerr << "                                  Found " <<  nKnots_ << ", expected at least 3 (to have at least 1 internal knot)" << std::endl;
 		gSystem->Exit(EXIT_FAILURE);
 	}
 
 	dydx_.assign(nKnots_,0.0);
 
 	a_.assign(nKnots_,0.0);
 	b_.assign(nKnots_,0.0);
 	c_.assign(nKnots_,0.0);
 	d_.assign(nKnots_,0.0);
 
 	this->calcDerivatives();
 }
 
 void Lau1DCubicSpline::calcDerivatives()
 {
 	switch ( type_ ) {
 		case SplineType::StandardSpline :
 			this->calcDerivativesStandard();
 			break;
 		case SplineType::AkimaSpline :
 			this->calcDerivativesAkima();
 			break;
 		case SplineType::LinearInterpolation :
 			//derivatives not needed for linear interpolation
 			break;
 	}
 }
 
 void Lau1DCubicSpline::calcDerivativesStandard()
 {
 	// derivatives are determined such that the second derivative is continuous at internal knots
 
 	// derivatives, k_i, are the solutions to a set of linear equations of the form:
 	// a_i * k_i-1  +  b_i * k+i  +  c_i * k_i+1  =  d_i with a_0 = 0, c_n-1 = 0
 
 	// this is solved using the tridiagonal matrix algorithm as on en.wikipedia.org/wiki/Tridiagonal_matrix_algorithm
 
 	// first and last equations give boundary conditions
 	// - for natural boundary, require f''(x) = 0 at end knot
 	// - for 'not a knot' boundary, require f'''(x) continuous at second knot
 	// - for clamped boundary, require predefined value of f'(x) at end knot
 
 	// non-zero values of a_0 and c_n-1 would give cyclic boundary conditions
 	a_[0] = 0.;
 	c_[nKnots_-1] = 0.;
 
 	// set left boundary condition
 	switch ( leftBound_ ) {
 		case BoundaryType::Natural :
 			{
 				b_[0] = 2./(x_[1]-x_[0]);
 				c_[0] = 1./(x_[1]-x_[0]);
 				d_[0] = 3.*(y_[1]-y_[0])/((x_[1]-x_[0])*(x_[1]-x_[0]));
 				break;
 			}
 
 		case BoundaryType::NotAKnot :
 			{
 				// define the width, h, and the 'slope', delta, of the first cell
 				const Double_t h1{x_[1]-x_[0]};
 				const Double_t h2{x_[2]-x_[0]};
 				const Double_t delta1{(y_[1]-y_[0])/h1};
 				const Double_t delta2{(y_[2]-y_[1])/h2};
 				// these coefficients can be determined by requiring f'''_0(x_1) = f'''_1(x_1)
 				// the requirement f''_0(x_1) = f''_1(x_1) has been used to remove the dependence on k_2
 				b_[0] = h2;
 				c_[0] = h1+h2;
 				d_[0] = delta1*(2.*h2*h2 + 3.*h1*h2)/(h1+h2) + delta2*5.*h1*h1/(h1+h2);
 				break;
 			}
 
 		case BoundaryType::Clamped :
 			{
 				b_[0] = 1.;
 				c_[0] = 0.;
 				d_[0] = dydx0_;
 				break;
 			}
 	}
 
 	// set right boundary condition
 	switch ( rightBound_ ) {
 		case BoundaryType::Natural :
 			{
 				a_[nKnots_-1] = 1./(x_[nKnots_-1]-x_[nKnots_-2]);
 				b_[nKnots_-1] = 2./(x_[nKnots_-1]-x_[nKnots_-2]);
 				d_[nKnots_-1] = 3.*(y_[nKnots_-1]-y_[nKnots_-2])/((x_[nKnots_-1]-x_[nKnots_-2])*(x_[nKnots_-1]-x_[nKnots_-2]));
 				break;
 			}
 		case BoundaryType::NotAKnot :
 			{
 				// define the width, h, and the 'slope', delta, of the last cell
 				const Double_t hnm1{x_[nKnots_-1]-x_[nKnots_-2]};
 				const Double_t hnm2(x_[nKnots_-2]-x_[nKnots_-3]);
 				const Double_t deltanm1{(y_[nKnots_-1]-y_[nKnots_-2])/hnm1};
 				const Double_t deltanm2{(y_[nKnots_-2]-y_[nKnots_-3])/hnm2};
 				// these coefficients can be determined by requiring f'''_n-3(x_n-2) = f'''_n-2(x_n-2)
 				// the requirement f''_n-3(x_n-2) = f''_n-2(x_n-2) has been used to remove
 				// the dependence on k_n-3
 				a_[nKnots_-1] = hnm2 + hnm1;
 				b_[nKnots_-1] = hnm1;
 				d_[nKnots_-1] = deltanm2*hnm1*hnm1/(hnm2+hnm1) + deltanm1*(2.*hnm2*hnm2 + 3.*hnm2*hnm1)/(hnm2+hnm1);
 				break;
 			}
 
 		case BoundaryType::Clamped :
 			{
 				a_[nKnots_-1] = 0.;
 				b_[nKnots_-1] = 1.;
 				d_[nKnots_-1] = dydxn_;
 				break;
 			}
 	}
 
 	// the remaining equations ensure that f_i-1''(x_i) = f''_i(x_i) for all internal knots
 	for(std::size_t i{1}; i<nKnots_-1; ++i) {
 		a_[i] = 1./(x_[i]-x_[i-1]);
 		b_[i] = 2./(x_[i]-x_[i-1]) + 2./(x_[i+1]-x_[i]);
 		c_[i] =                      1./(x_[i+1]-x_[i]);
 		d_[i] = 3.*(y_[i]-y_[i-1])/((x_[i]-x_[i-1])*(x_[i]-x_[i-1])) + 3.*(y_[i+1]-y_[i])/((x_[i+1]-x_[i])*(x_[i+1]-x_[i]));
 	}
 
 	// forward sweep - replace c_i and d_i with
 	//
 	// c'_i =  c_i /  b_i                 for i = 0
 	//         c_i / (b_i - a_i * c_i-1)  otherwise
 	//
 	// and
 	//
 	// d'_i =   d_i                /  b_i                 for i = 0
 	//         (d_i - a_i * d_i-1) / (b_i - a_i * c_i-1)  otherwise
 
 	c_[0] /= b_[0];
 	d_[0] /= b_[0];
 
 	for(std::size_t i{1}; i<nKnots_-1; ++i) {
 		c_[i] =  c_[i]                  / (b_[i] - a_[i]*c_[i-1]);
 		d_[i] = (d_[i] - a_[i]*d_[i-1]) / (b_[i] - a_[i]*c_[i-1]);
 	}
 
 	d_[nKnots_-1] = (d_[nKnots_-1] - a_[nKnots_-1]*d_[nKnots_-2]) / (b_[nKnots_-1] - a_[nKnots_-1]*c_[nKnots_-2]);
 
 	// back substitution - calculate k_i = dy/dx at each knot
 	//
 	// k_i = d'_i                   for i = n-1
 	//       d'_i - c'_i * k_i+1    otherwise
 
 	dydx_[nKnots_-1] = d_[nKnots_-1];
 
 	for(int i {static_cast<int>(nKnots_-2)}; i>=0; --i) {
 		dydx_[i] = d_[i] - c_[i]*dydx_[i+1];
 	}
 }
 
 void Lau1DCubicSpline::calcDerivativesAkima() {
 	//derivatives are calculated according to the Akima method
 	// J.ACM vol. 17 no. 4 pp 589-602
 
 	Double_t am1{0.0}, an{0.0}, anp1{0.0};
 
 	// a[i] is the slope of the segment from point i-1 to point i
 	//
 	// n.b. segment 0 is before point 0 and segment n is after point n-1
 	//      internal segments are numbered 1 - n-1
 	for(std::size_t i{1}; i<nKnots_; ++i) {
 		a_[i] = (y_[i]-y_[i-1])/(x_[i]-x_[i-1]);
 	}
 
 	// calculate slopes between additional points on each end according to the Akima method
 	// method assumes that the additional points follow a quadratic defined by the last three points
 	// this leads to the relations a[2] - a[1] = a[1] - a[0] = a[0] - a[-1] and a[n-1] - a[n-2] = a[n] - a[n-1] = a[n+1] - a[n]
 	a_[0]         = 2*a_[1]         - a_[2];
 	am1           = 2*a_[0]         - a_[1];
 
 	an            = 2*a_[nKnots_-1] - a_[nKnots_-2];
 	anp1          = 2*an            - a_[nKnots_-1];
 
 	// b[i] is the weight of a[i]   towards dydx[i]
 	// c[i] is the weight of a[i+1] towards dydx[i]
 	// See Appendix A of J.ACM vol. 17 no. 4 pp 589-602 for a justification of these weights
 	b_[0] = TMath::Abs(a_[1] - a_[0]);
 	b_[1] = TMath::Abs(a_[2] - a_[1]);
 
 	c_[0] = TMath::Abs(a_[0] - am1  );
 	c_[1] = TMath::Abs(a_[1] - a_[0]);
 
 	for(std::size_t i{2}; i<nKnots_-2; ++i) {
 		b_[i] = TMath::Abs(a_[i+2] - a_[i+1]);
 		c_[i] = TMath::Abs(a_[i]   - a_[i-1]);
 	}
 
 	b_[nKnots_-2] = TMath::Abs(an            - a_[nKnots_-1]);
 	b_[nKnots_-1] = TMath::Abs(anp1          - an           );
 
 	c_[nKnots_-2] = TMath::Abs(a_[nKnots_-2] - a_[nKnots_-3]);
 	c_[nKnots_-1] = TMath::Abs(a_[nKnots_-1] - a_[nKnots_-2]);
 
 	// dy/dx calculated as the weighted average of a[i] and a[i+1]:
 	// dy/dx_i = ( | a_i+2 - a_i+1 | a_i  +  | a_i - a_i-1 | a_i+1 ) / ( | a_i+2 - a_i+1 |  +  | a_i - a_i-1 | )
 	// in the special case a_i-1 == a_i != a_i+1 == a_i+2 this function is undefined so dy/dx is then defined as (a_i + a_i+1) / 2
 	for(std::size_t i{0}; i<nKnots_-2; ++i) {
 		if(b_[i]==0 && c_[i]==0) {
 			dydx_[i] = ( a_[i] + a_[i+1] ) / 2.;
 		} else {
 			dydx_[i] = ( b_[i] * a_[i] + c_[i] * a_[i+1] ) / ( b_[i] + c_[i] );
 		}
 	}
 
 	if(b_[nKnots_-1]==0 && c_[nKnots_-1]==0) {
 		dydx_[nKnots_-1] = ( a_[nKnots_-1] + an ) / 2.;
 	} else {
 		dydx_[nKnots_-1] = ( b_[nKnots_-1] * a_[nKnots_-1] + c_[nKnots_-1] * an ) / ( b_[nKnots_-1] + c_[nKnots_-1] );
 	}
 }
diff --git a/test/TestReadSplineFromJson.cc b/test/TestReadSplineFromJson.cc
index 3c18643..04a477b 100644
--- a/test/TestReadSplineFromJson.cc
+++ b/test/TestReadSplineFromJson.cc
@@ -1,38 +1,46 @@
 #include <memory>
 
 #include "TF1.h"
 #include "TCanvas.h"
 
 #include "Lau1DCubicSpline.hh"
 
 void loadUnnamedSpline()
 {
-	Lau1DCubicSpline dtEffSpline{ Lau1DCubicSpline::readFromJson("test-write-noname.json") };
+	auto dtEffSpline = Lau1DCubicSpline::readFromJson("test-write-noname.json");
+	if ( not dtEffSpline ) {
+		std::cerr << "nullptr returned from reading \"test-write-noname.json\"" << std::endl;
+		return;
+	}
 
-	std::unique_ptr<TF1> tf1 { dtEffSpline.makeTF1() };
+	auto tf1 = dtEffSpline->makeTF1();
 
 	TCanvas canvas("canvas","canvas",800,450);
 
 	tf1->Draw();
 
 	canvas.SaveAs("loadedUnnamedSpline.png");
 }
 
 void loadNamedSpline()
 {
-	Lau1DCubicSpline dtEffSpline{ Lau1DCubicSpline::readFromJson("test-write-named.json","spline2") };
+	auto dtEffSpline = Lau1DCubicSpline::readFromJson("test-write-named.json","spline2");
+	if ( not dtEffSpline ) {
+		std::cerr << "nullptr returned from reading \"spline2\" from \"test-write-named.json\"" << std::endl;
+		return;
+	}
 
-	std::unique_ptr<TF1> tf1 { dtEffSpline.makeTF1() };
+	auto tf1 = dtEffSpline->makeTF1();
 
 	TCanvas canvas("canvas","canvas",800,450);
 
 	tf1->Draw();
 
 	canvas.SaveAs("loadedNamedSpline.png");
 }
 
 int main()
 {
 	loadUnnamedSpline();
 	loadNamedSpline();
 }